The £9m-rated 22-year-old Dutch striker has scored nine goals in 13 appearances this season and has also attracted the interest of Chelsea.

"I know they (Manchester United and Chelsea) are watching him but that is not unusual because they are watching all the best young players in Europe," his agent Louis Laros told the International Business Times.

"I have not spoken to anyone about his future. At the moment any interest is only rumours and nothing more."